linux-kernel - Re: [PATCH v2 4/13] Audit: maintain an lsmblob in audit

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Message-ID: <56cfa89c-1a62-4c48-a67a-186226de1843@schaufler-ca.com>
Date: Tue, 3 Sep 2024 18:18:42 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Paul Moore <paul@...l-moore.com>, linux-security-module@...r.kernel.org
Cc: jmorris@...ei.org, serge@...lyn.com, keescook@...omium.org,
 john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
 stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
 selinux@...r.kernel.org, mic@...ikod.net,
 Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v2 4/13] Audit: maintain an lsmblob in audit_context

On 9/3/2024 5:18 PM, Paul Moore wrote:
> On Aug 29, 2024 Casey Schaufler <casey@...aufler-ca.com> wrote:
>> Replace the secid value stored in struct audit_context with a struct
>> lsmblob. Change the code that uses this value to accommodate the
>> change. security_audit_rule_match() expects a lsmblob, so existing
>> scaffolding can be removed. A call to security_secid_to_secctx()
>> is changed to security_lsmblob_to_secctx().  The call to
>> security_ipc_getsecid() is scaffolded.
>>
>> A new function lsmblob_is_set() is introduced to identify whether
>> an lsmblob contains a non-zero value.
>>
>> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
>> ---
>>  include/linux/security.h | 13 +++++++++++++
>>  kernel/audit.h           |  3 ++-
>>  kernel/auditsc.c         | 19 ++++++++-----------
>>  3 files changed, 23 insertions(+), 12 deletions(-)
>>
>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index 457fafc32fb0..a0b23b6e8734 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -277,6 +277,19 @@ static inline const char *kernel_load_data_id_str(enum kernel_load_data_id id)
>>  	return kernel_load_data_str[id];
>>  }
>>  
>> +/**
>> + * lsmblob_is_set - report if there is a value in the lsmblob
>> + * @blob: Pointer to the exported LSM data
>> + *
>> + * Returns true if there is a value set, false otherwise
>> + */
>> +static inline bool lsmblob_is_set(struct lsmblob *blob)
>> +{
>> +	const struct lsmblob empty = {};
>> +
>> +	return !!memcmp(blob, &empty, sizeof(*blob));
>> +}
>> +
>>  #ifdef CONFIG_SECURITY
> We probably want a !CONFIG_SECURITY variant of this too.

I'll check, but I expect you're right.

>
>>  int call_blocking_lsm_notifier(enum lsm_event event, void *data);
>> diff --git a/kernel/audit.h b/kernel/audit.h
>> index a60d2840559e..b1f2de4d4f1e 100644
>> --- a/kernel/audit.h
>> +++ b/kernel/audit.h
>> @@ -11,6 +11,7 @@
>>  
>>  #include <linux/fs.h>
>>  #include <linux/audit.h>
>> +#include <linux/security.h>
>>  #include <linux/skbuff.h>
>>  #include <uapi/linux/mqueue.h>
>>  #include <linux/tty.h>
>> @@ -160,7 +161,7 @@ struct audit_context {
>>  			kuid_t			uid;
>>  			kgid_t			gid;
>>  			umode_t			mode;
>> -			u32			osid;
>> +			struct lsmblob		oblob;
>>  			int			has_perm;
>>  			uid_t			perm_uid;
>>  			gid_t			perm_gid;
>> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
>> index 23adb15cae43..84f6e9356b8f 100644
>> --- a/kernel/auditsc.c
>> +++ b/kernel/auditsc.c
>> @@ -724,9 +724,7 @@ static int audit_filter_rules(struct task_struct *tsk,
>>  				/* Find ipc objects that match */
>>  				if (!ctx || ctx->type != AUDIT_IPC)
>>  					break;
>> -				/* scaffolding */
>> -				blob.scaffold.secid = ctx->ipc.osid;
>> -				if (security_audit_rule_match(&blob,
>> +				if (security_audit_rule_match(&ctx->ipc.oblob,
>>  							      f->type, f->op,
>>  							      f->lsm_rule))
>>  					++result;
>> @@ -1394,19 +1392,17 @@ static void show_special(struct audit_context *context, int *call_panic)
>>  			audit_log_format(ab, " a%d=%lx", i,
>>  				context->socketcall.args[i]);
>>  		break; }
>> -	case AUDIT_IPC: {
>> -		u32 osid = context->ipc.osid;
>> -
>> +	case AUDIT_IPC:
>>  		audit_log_format(ab, "ouid=%u ogid=%u mode=%#ho",
>>  				 from_kuid(&init_user_ns, context->ipc.uid),
>>  				 from_kgid(&init_user_ns, context->ipc.gid),
>>  				 context->ipc.mode);
>> -		if (osid) {
>> +		if (lsmblob_is_set(&context->ipc.oblob)) {
>>  			char *ctx = NULL;
>>  			u32 len;
>>  
>> -			if (security_secid_to_secctx(osid, &ctx, &len)) {
>> -				audit_log_format(ab, " osid=%u", osid);
>> +			if (security_lsmblob_to_secctx(&context->ipc.oblob,
>> +						       &ctx, &len)) {
>>  				*call_panic = 1;
>>  			} else {
>>  				audit_log_format(ab, " obj=%s", ctx);
>> @@ -1426,7 +1422,7 @@ static void show_special(struct audit_context *context, int *call_panic)
>>  				context->ipc.perm_gid,
>>  				context->ipc.perm_mode);
>>  		}
>> -		break; }
>> +		break;
>>  	case AUDIT_MQ_OPEN:
>>  		audit_log_format(ab,
>>  			"oflag=0x%x mode=%#ho mq_flags=0x%lx mq_maxmsg=%ld "
>> @@ -2642,7 +2638,8 @@ void __audit_ipc_obj(struct kern_ipc_perm *ipcp)
>>  	context->ipc.gid = ipcp->gid;
>>  	context->ipc.mode = ipcp->mode;
>>  	context->ipc.has_perm = 0;
>> -	security_ipc_getsecid(ipcp, &context->ipc.osid);
>> +	/* scaffolding */
>> +	security_ipc_getsecid(ipcp, &context->ipc.oblob.scaffold.secid);
>>  	context->type = AUDIT_IPC;
>>  }
>>  
>> -- 
>> 2.46.0
> --
> paul-moore.com
>